Myntra.com — regarding wrong delivery of dress material

I have ordered a dress at myntra on 23rd september against which a different dress material have been delivered to me on 3rd october, 2018. I had complaint this to myntra on same day evening giving all the details. Now, the material has been received by myntra on 9th october, 2018 and i have received a message that "your refund of rs 782.25 against order no.[protected]-8403101 could not be processed" in my mobile no. [protected]. Now, my question is that why an amount of rs 782.25 is being refunded by myntra, whereas i have paid an amount rs 931.00 against the dress material. The material which i have returned to myntra is due to wrong delivery by myntra, then why myntra is returning less amount applying their "return policy". It is a matter of great regret that such kind of act will reduce the tendency of online marketing. I strongly oppose what myntra has done with me and will never purchase anything from myntra.